Electric-arc welding control method and means



Nov. 8, 1927.

H. D. MORTON ELECTRIC ARC WELDING CONTROL METHOD AND MEANS OriginalFiled Jan. 27, 1917 INVENTOR.

W 0%. 01 mm Patented Nov. 8, i927.

PArsNr HARRY I). MORTON, OF NEW 'YQRK, N. Y.,

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ASSIGNOR 0 AUTOMATIC ABC 'WELDING MICHIGAZI, A CORPORATION OF MICHIGAN.

ELECTRIC-ARC WELDING CGN'I'ROL METHOD AND MEANS.

Original application riled January 27, 1917, Serial No. 144,930. BenewedAugust 14, 1917, Serial 1T0. 186,238. Divided and this application filedAugust 20, 1927. Serial No. 214,263.

sponse to a variable characteristic of the welding circuit.

The followingis' a description of electric arc welding control methodsand means embodying the invention in its present preferred form, but itwill be understood that various modifications and changes may be madetherein without departing from the spirit of the invention and withoutexceeding the scope of the claims,

The invention will best be understood by reference to the accompanyingdrawing wherein is a diagrammatic illustration of a system and meansembodying the present invention.

I have foundthat it is essential for the practical successful operationof this form of electric arc welding that an equilibrium be maintainedbetween the rate of fusing of a strip of welding material and the rateat which said weldin material is fed to the arc. I have foun that'undersome conditions and within-narrow limits this equilibrium is maintainedby the arc itself which has, within certain limits, it the welding stripis continuously fed at a suitable constant rate, a compensatory actionas follows: when the arc shortens the resistance decreases, the amperagerises, and this rise in amperage results in the welding strip fusingmore rapidly, thereby causing the arc to lengthen, Conversely, if theare lengthens the resistance is increased, the amperage decreasesproportionately, the welding strip is fused more slowly and thecontinuously moving welding strip restores the arc to its normal length.

While as I have stated this compensatory action of the are may maintainthe necessary equilibrium between the rate of fusing and the rate ofwelding strip feed, this applies work and the welding head while onlywithin relatively narrow limits. I have found in practice that dueperhaps to differences in the fusibility or conductivity of the weldingstrip or of the work it frequently occurs that the range of compensatoryaction of the arc is insutficient to prevent either a contacting of thewelding strip with the work or a rupture of the are due to its becomingtoo long.

To overcome this difiiculty I have devised a method and system by meansof which the equilibrium is maintained within any desired limit bycontrolling the rate at which the welding strip is fed to the are.

Referring to the drawing, G represents an electric generator forsupplying electric welding current to the welding circuit which includeswire 75, welding strip 14, are a, work 15, wires 76 and 77 to generatorG. The wire feed rolls 19 and 20 may be driven by an electric motor M,which motor derives its current from generator G by Wires 75, 78 and 79.Generator G is shown as driven by a gasoline engine E.

The feeding mechanism for ieeding the metallic Welding strip 14 to thework 15 consists of'two feed rollers 19 and 20, preferably provided withserrated perimeters, located to receive between them the welding strip14 which is in the form of a Wire. The feed rolls 19 and 20 are I in awelding head 21 which is indicated in dotted lines and provided withsuitable guides for the welding strip 14:. The feed rolls may be gearedtogether. The work 15 consists of two cylindrical members which are tobe joined by an annular weld and in order to do this the work is rotatedwhile the welding strip is fedto the are at a and while the molten metalformed is being deposited in the groove. The cylindrical memersconstituting the work 15 are rotatably supported in some suitable manneras by the center 26 and the mandrel 27. The mandrel 27 is connected bythe gear 81 to a gear 80 keyed to shaft m of motor M. It will be seenthat by this arrangement the motor M drives the feed rolls 19 and 2G andalso produces a relative movement between the the strip rotatablymounted 14 is being fed to the work and the molten metal is beingdeposited on the work. It will also be noted that the feed rollsaredriven at a higher speed than the work, since i the ratio of the gears80' and 81 is about fuses very rapidly there is a danger that the are ata may suddenly become so long as to rupture and then in order to startthe are it is necessary to bring the end of the strip 14' again intocontact with the work. Conversely, if the feed of the strip 14 to theare a is more rapid than the fusion of the welding strip, the weldingstrip may be fed against the work and cause a short circuit which isinjurious to the work and also requires separating the electrodestoagain form an arc.

As heretofore explained the are a has a compensatory action so thatwithin narrow limits the differences in the fusibility of the weldingstrip 14 will be automatically taken care of by the arc itself. However,in order to take care of the extreme differences of fusibility of thewelding strip and irregularities in the contour of the work and therebymaintain the are I have devised an automatic control mechanism which isresponsive to the changes in the amperage of the are a resulting fromthe varying rate of melting of the welding strip and from irregularitiesin the contour of thework; and which will alter the rate of feed of thewelding strip 14 to correct the variations of the arc and thuscompensate for the differences in fusibility of the feeding strip.

In this system my method would be carriedout in the following manner. Asthe are at a shortens its resistance decreases, the amperage increasesand as this amperage represents the load upon the prime mover, i. e. thegasoline engine E, the speed of such prime mover will be decreased. Thisdecrease in speed will, of course, result in a corresponding decrease inthe speed of the electric generator G driven by said prime mover. Thisdecrease in generator speed results in the lowering of the generatorvoltage. As the motor M which drives the feed rolls derives its currentfrom the generator G it will be aifected by the drop in generatorvoltage and its speed and consequently the rate of the welding stripfeed will be reduced. This decrease in the rate of the welding stripfeed will result in the are being gradually restored to its normallength.

. This will reduce the load upon the prime mover E, allowing its speedto become normal, restoring the normal speed and voltage e of thegenerator G and consequently of t motdor' M and of the rate of weldingstrip fee Conversely, if the arc becomes too long its resistanceincreases, the amperage decreases, the load on the prime mover Edecreases, causing the speed of the gasoline engine E together with thatof the generator G to increase. I causes a corresponding increase ingenerator voltage which results in motor M running at a higher speed,feeding the welding strip 14 to the are more rapidly and graduallyrestoring the arc to its normal length.-

This increase in generator speed motor deriving its current from agenerator 1 supplying welding current and driven by any source of powersufficiently responsive in rate of speed to variations in load, i. e.variations in amperage of the are, my method will be operative.

It is to be understood that the system here shown is merely illustrativeand that the well-known arc-starting devices, ballistic resistances,reactances, and manipulating means such as switches, etc., common in theart, are omitted; and that numerous other systems may be employed forcarrying out the same method and obtaining the same results.

- It is to be understood that when the contour of the work varies, it'is necessary. to vary the relation between the fusing rate and thefeeding rate of the strip. For instance, if an elevation or protuberancein the work is encountered, it then becomes necessary to fuse the stripfaster than it is fed. On the other hand, if a depression in the work isencountered, it becomes necessary to feed the strip faster than it isfused.

By the term a characteristic of. the are used in the claims, I intend toinclude such variable, utilizable properties as accompany the operationof an arc, and which are indicative of its normal orabnormal o ration,such, for example, as" its current, vo tage, resistance, length, orenergy absorption.

I claim:

' 1. The method of electrical arc welding which consists in applyingmolten metal derived from one electrode fed toward the other electrode,varying the speed of. the motive power of the generator which furnishescurrent to the'arc, such-speed variations being in response to changesin arc length, and correctively altering the feeding rate of theelectrode in response to such variations in speed.

2. The method of preventing extinction of a metallic arc during theprocess of welding which consists in supplying said are with currentfrom a generator driven by a motive power which responds in speed tovariations in arc length, feeding an electrode to the arc, andvaryingthe feeding rate of the electrode in response to changes in speed ofsuch motive power.

3. In a metallic electrode electrical arc welding machine in which thework constitutes one electrode and a welding strip the other electrode,the combination of a generator for supplying welding current, motivepower for said generator responsive in speed to changes in arc length,means for feeding the welding strip to the arc. and means responsive tovariations in speed of said motive power for changing the feeding rateof the welding strip in order to maintainthe arc.

4. In an electric arc welding machine in which a welding stripconstitutes one electrode and the work constitutes the other electrode,the combination of an electric motor driving a mechanism for feeding thewelding strip toward the work, a generator from which said motor derivesits current, which said generator also supplies current to the weldingcircuit, and a motive power for said generator responsive in its rate ofspeed to variations in load on the welding circuit. 5. In an arc weldingapparatus, a source of electric energy, a welding circuit including saidsource, a welding strip, work material and a motor, said motor beingconstructed and arranged to continuously feed the welding strip to anarc struck between the welding strip and the work and being responsivein speed to a variable characteristic of the said circuit.

6. In an arc welding apparatus, a welding circuit including'a weldingstrip, work material and a source of electric energy for supplyingcurrent to the arc, and a dynamoelectric motor for feeding the weldingstrip to the work to maintain the arc length substantially constant,said motor being connected to said welding circuit and being responsivein speed to a variable characteristic of said circuit.

7. In an arc welding apparatus, a source of electric energy forsupplying current to the arc, a welding circuit connected to said sourcein which circuit an arc is adapted to be struck between a welding penciland work material, and a dynamo-electric motor connected to said sourceof energy for feeding said welding pencil to the arc, said motor beingresponslve in speed to conditions inthe welding circuit.

. 8. In electric arc welding wherein the work constitutes one electrodeand-a welding pencil constitutes the other electrode, the combination ofa welding circuit including said welding pencil and work material, afeeding mechanism for said weldin pencil, and a rotatable motorconnected to t e welding circuit and responsive in speed to conditionsin said circuit for actuating said feeding mechanism.

9. An apparatus for metallic arc welding of the type wherein the weldingarc is maintainedbetween the work and a metallic electrode, and whereinelectrode feedin mechanism is arranged to be operated to Ieed theelectrode to maintain the arc, and wherein a variable-speeddynamo-electric machineconnected to the welding circuit is arranged tooperate said feeding mechanism, characterized by the fact that the speedof said dynamo-electric machine is automatically con trolled inaccordance with a variable characteristic of the welding circuit.

10. In electric arc welding, a welding circuit including a weldingpencil and work material between which an arc is adapted to be struck,feeding mechanism for the welding pencil, and a continuously operatingmotor connected tosaid circuit and responsive in speed to variations inarc length for actuating said feeding mechanism.

HARRY D. MORTON.

